It's already joint using Mitre mate. The guy couldn't get the gap any closer so it's the cut that he messed up on.
Surely all you have to do is to undo side of the cornice and slide it up, better to have a small gap either next to the wall that can be filled
Great minds - but just the think the OP is ignoring all the solutions. BTW should have started my post with "Oh for heavens sake ...."
I thought the trim was ivory colour so wouldn't using white (anything) to cover the cut just highlight the problem ?
no, I've recently moved in. Why wouldn't the chalk last? Not like I'll be scrubbing the wardrobe down!
Dry flex resin filler. 2 will become one and never crack, but will need to paint after. Really need to find a painter local that got some as not cheap to buy for such a small bit